1. Field of the Invention
The present disclosure relates to an image forming apparatus, and to a process cartridge and a developing device used in the image forming apparatus.
The image forming apparatus forms an image on a recording medium using, for example, an electrophotographic method. The process cartridge includes a cartridge provided by the integration of an image bearing member and a process unit acting upon the image bearing member, and is detachably attachable to an apparatus main body of the image forming apparatus. The developing device supplies a developer to a latent image formed on the image bearing member in the apparatus main body to form a visible image.
2. Description of the Related Art
In an image forming apparatus such as a laser beam printer and a copying machine, a contact developing method has been widely used for development of an image by causing a developer bearing member to contact a photosensitive member serving as an image bearing member. In such a contact developing method, there are cases where a developing roller having an elastic layer is used as a developer bearing member. Conventionally, a plate-like developing blade serving as a developer regulating member is caused to contact a developing roller so that the amount of toner carried by the developing roller is regulated. A thin toner layer is formed on the developing roller by the developing blade, and an electrostatic latent image formed on the photosensitive member contacts such a thin toner layer, so that a high quality toner image is formed.
Generally, the developing blade is fixed in a state of pressing the developing roller with a predetermined pressure. However, Japanese Patent Application Laid-Open No. 8-254895 discusses a developing device including a movable developing blade and a driving solenoid for moving the developing blade. For example, when a foreign substance is sandwiched between the developing blade and the developing roller, the developing blade is separated from the developing roller, so that the foreign substance can be removed.
Herein, if the developing blade constantly presses the developing roller for a long time, a blade mark may be generated on the developing roller. Such a blade mark can lead to deformation of the developing roller. Conventionally, such deformation is relatively small and not considered as a problem. However, a developing roller has been expected to reduce deformation thereof over the lapse of time to meet a recent demand for high quality images.
Although the separation of the developing blade from the developing roller as discussed in Japanese Patent Application Laid-Open No. 8-254895 can suppress deformation of the developing roller over the time, a drive unit needs to be disposed to move the developing blade. Such a configuration may increase complexity of the image forming apparatus.